Thermoplastic polyurethanes for use in adhesives are known in the art. According to the Handbook of Pressure Sensitive Adhesive Technology, 2nd ed., 1989, edited by Donatas Satas, page 523, polyurethanes have attracted a considerable amount of development effort for various types of pressure sensitive adhesives, but the applications so far have been limited to low tack, low peel adhesive protective liners.
Further, it is known from e.g. U.S. Pat. No. 3,437,622 that thermoset reaction products of polyols with aromatic polyisocyanates compounded with tackifying resins and plasticizers can be used for high-temperature-resistant masking tapes.
European patent application publication No. 0 709 416 describes pressure sensitive adhesives which contain thermoset polyurethanes. In one embodiment the polyurethanes are prepared from a polyisocyanate having a functionality of from 2.2 to 10 and a mixture of a hydrogenated polydiene mono-ol and a hydrogenated polydiene diol.
However, there is a need for thermoplastic pressure sensitive adhesives which can be used at high temperatures. Further, there is a need for a thermoplastic polyurethane-based pressure sensitive adhesives having better tack and cohesion properties, while exhibiting enhanced stability.
Surprisingly, thermoplastic polyurethane-based pressure sensitive adhesives have now been found which solve one or more problems encountered with known pressure sensitive adhesives. In particular, thermoplastic polyurethane-based pressure sensitive adhesives have been found which have better tack and cohesive properties and can be used up to high temperatures.